Hydrogenolysis of polyhydric alcohols obtained from the natural world using a catalyst for converting the polyhydric alcohols into other compounds is an important technique from the viewpoint of effective utilization of materials or substances.
On the other hand, production of glycerol used as the polyhydric alcohol in food or medical applications has been increased year by year. One of the reasons therefor is the spread of bio-diesel fuels which have recently come to dominate owing to uncertain supply of fossil fuels or global warming problems. Glycerol is produced during the process for production of the bio-diesel fuels from raw vegetable materials. However, excessive supply of the glycerol has occurred due to currently limited applications thereof. Therefore, effective utilization of the glycerol has been demanded. As one solution of the above problem, a catalytic reaction of the glycerol for converting the glycerol into C3 alcohols has been noticed over the world.
The C3 alcohols are useful as various industrial materials, etc. Among the C3 alcohols, as diols, there are 1,3-propanediol and 1,2-propanediol. The 1,3-propanediol has been noticed as a raw material of polyesters and polyurethanes, etc.
On the other hand, the 1,2-propanediol has been used, for example, for production of polyester resins, paints, alkyd resins, various plasticizers, anti-freezing fluids, brake oils, etc., and further are useful for production of food wetting agents, viscosity increasers for fruit juices, cellophane softeners for food, cosmetics, drugs, etc.
In the circumstances, in order to effectively utilize glycerol, it has been considered to convert glycerol into propanediols, and there are therefore known various methods for producing 1,2-propanediol (hereinafter occasionally referred to merely as “1,2-PD”) by hydrogenolysis of the glycerol.
For example, as the fixed-bed continuous liquid phase reaction methods, there are known (1) the method using a copper-chromium catalyst (for example, refer to Patent Document 1), (2) the method using a cobalt-copper-manganese-molybdenum catalyst (for example, refer to Patent Document 2), (3) the method using a copper-zinc-aluminum catalyst (for example, refer to Patent Document 3), (4) the method using a nickel-rhenium catalyst (for example, refer to Patent Document 4), (5) the method using a copper catalyst (for example, refer to Patent Document 5), etc.
In these fixed-bed continuous liquid phase reaction methods, a hydrogenation reaction may be generally carried out in a liquid phase using a solvent. As far as a hydrogenolysis of glycerol is concerned, in any of Patent Documents 1 to 5, water is used as the solvent. In these Patent Documents, there are described the reaction examples using water in an amount of 10% by mass or more. Specifically, in Patent Document 2, there is described the reaction example using water in an amount of 13.5% by mass or more, and in Patent Document 5, there is described the reaction example using water in an amount of 10% by mass or more. Incidentally, it is also described that in the fixed-bed continuous liquid phase methods (for example refer to Patent Document 6), the effect of protecting a catalyst is attained by using water as the solvent.
Patent Document 1: DP-A 4302464
Patent Document 2: EP-A 713849
Patent Document 3: EP-A 523015
Patent Document 4: PCT Pamphlet WO 03/035582
Patent Document 5: PCT Pamphlet WO 07/099,161
Patent Document 6: PCT Pamphlet WO 07/010,299